1. Field of the Invention
This invention relates to thread cutting apparatus, and, more particularly, to thread cutting apparatus for vertical milling machines.
2. Description of the Prior Art
U.S. Pat. No. 1,946,214 (Kabigting) discloses a drill with a frame for the drill which allows the drill to be used as a drill press. A spindle is secured to the frame and is used in place of the original drill spindle. The spindle includes different pitch thread portions, and two different split nuts are used with the respective portions of different pitch. The split nuts are actuated into and out of engagement with the spindle by means of cams and springs. The speed at which the drill penetrates the work depends on which nut and which threaded portion are in engagement.
U.S. Pat. No. 2,001,057 (Fellay) discloses a drill system utilizing a lead screw and split nut elements. The engaging and disengaging of the split nut elements with the lead screw is manually accomplished. Rotation of the box housing, with the split nuts engaged, causes rotation of the screw. With the half nuts disengaged, rotation of the housing has no effect on the lead screw.
U.S. Pat. No. 3,365,735 (Brown) discloses a thread tapping apparatus which uses a screw and a nut system to advance the tap. The screw threads are secured for vertical movement to a sleeve disposed on a splined shaft. The shaft is in turn secured to a motor. Vertical movement of the tap occurs only when the threads are coupled to the split nuts. Otherwise, rotary motion only, without any vertical motion, takes place.
U.S. Pat. No. 3,661,470 (O'Pry) discloses a power takeoff system utilizing a lead screw connected to a drive system. Split nut segments are hydraulically coupled to and from the lead screw to control the advancement of a tool relative to the drive system. A threaded shaft is secured to the power takeoff system, and split nuts engage the threaded shaft to cause rotation of the tool for cutting threads. When the split nut elements are disengaged from the threaded shaft, no longitudinal movement of the tool takes place.
U.S. Pat. No. 4,480,700 (Krieger et al) discloses a boring device utilizing a split nut assembly to engage a lead screw for forcing engagement between the boring tool and the work. The engagement of the split nut elements with the lead screw is controlled so as to control the movement of the tool. Release of the split nuts from the lead screw disengages the tool when the desired depth of cut has been made.
All of the above-discussed patents utilize, in some fashion, the concept of a threaded lead screw, sleeve, etc., engageable by split nuts to cause movement of the lead screw. Upon release of the threaded nuts with the threaded shaft or sleeve, movement, along the axis of the shaft, etc., ceases. In some cases rotary motion continues, but axial movement, either vertical or horizontal, stops with the disengagement of the split nut elements from the lead screw or threaded element.
Drilling or thread cutting or the like is accomplished with the engagement of the split nuts with the threaded shaft or sleeve. Some degree of controlled axial movement is accomplished by a tool with respect to work. However, the engagement or disengagement of the split nuts with the threaded element is generally manually accomplished. Moreover, it will be noted that some of the apparatus disclosed in the patents is relatively complicated, and thus relatively expensive.
The apparatus of the present invention is relatively simple, and the disengagement of split nut elements from a threaded sleeve may be accomplished automatically with a relatively simple cam release system. Engagement between the split nut elements and the threaded sleeve is manually accomplished. The apparatus allows internal or external threads of any desired pitch and any desired thread style to be accomplished in a relatively simple and inexpensive manner.